Ewingite: Earth’s most complex mineral

Olds, Travis A.; Plášil, Jakub; Kampf, Anthony R.; Simonetti, Antonio; Sadergaski, Luke R.; Chen, Yu‐Sheng; Burns, Peter C.

doi:10.1130/g39433.1

Cited by 30 publications

(31 citation statements)

References 28 publications

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“…However, the unit cell volume of andersonite is 1.5 times bigger and the high complexity parameters for liebigite are governed by double the amount of H 2 O molecules. For comparison, the crystal structures of rutherfordine, (UO 2 )(CO 3 ) [11], should be considered as very simple (2.236 bits/atom and 15.651 bits/cell), while another uranyl carbonate mineral, ewingite, Mg 8 Ca 8 (UO 2 ) 24 (CO 3 ) 30 O 4 (OH) 12 ·138(H 2 O) [9], is the most complex mineral known (12,684.86 bits/cell without H-atoms correction).…”

Section: Discussionmentioning

confidence: 99%

“…Currently, there are almost 40 known uranyl carbonate mineral species. From the perspective of crystallography, this group of compounds is of considerable interest mainly due to the recent discoveries of the structurally highly complex minerals ewingite, Mg 8 Ca 8 (UO 2 ) 24 (CO 3 ) 30 O 4 (OH) 12 ·138(H 2 O) [9] and paddlewheelite, MgCa 5 Cu 2 (UO 2 ) 4 (CO 3 ) 12 ·33(H 2 O) [10]. However, members of this family are often challenging for research due to low crystallinity; crystal structures of about half of the uranyl carbonate minerals are still undetermined.…”

Section: Introductionmentioning

confidence: 99%

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Structure Refinement and Thermal Stability Studies of the Uranyl Carbonate Mineral Andersonite, Na2Ca[(UO2)(CO3)3]·(5+x)H2O

et al. 2018

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A sample of uranyl carbonate mineral andersonite, Na 2 Ca[(UO 2 )(CO 3 ) 3 ]·5−6H 2 O, originating from the Cane Springs Canyon, San Juan Co., UT, USA was studied using single-crystal and powder X-ray diffraction at various temperatures. Andersonite is trigonal, R−3m, a = 17.8448(4), c = 23.6688(6) Å, V = 6527.3(3) Å 3 , Z = 18, R 1 = 0.018. Low-temperature SCXRD determined the positions of H atoms and disordered H 2 O molecules, arranged within the zeolite-like channels. The results of high-temperature PXRD experiments revealed that the structure of andersonite is stable up to 100 • C; afterwards, it loses crystallinity due to release of H 2 O molecules. Taking into account the well-defined presence of H 2 O molecules forming channels' walls that to the total of five molecules p.f.u., we suggest that the formula of andersonite is Na 2 Ca[(UO 2 )(CO 3 ) 3 ]·(5+x)H 2 O, where x ≤ 1. The thermal behavior of andersonite is essentially anisotropic with the lowest values of the main thermal expansion coefficients in the direction perpendicular to the channels (plane (001)), while the maximal expansion is observed along the c axis-in the direction of channels. The thermal expansion around 80 • C within the (001) plane becomes negative due to the total release of "zeolitic" H 2 O molecules. The information-based structural complexity parameters of andersonite were calculated after the removal of all the disordered atoms, leaving only the predominantly occupied sites, and show that the crystal structure of the mineral should be described as complex, possessing 4.535 bits/atom and 961.477 bits/cell, which is comparative to the values for another very common natural uranyl carbonate, liebigite.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Structure Refinement and Thermal Stability Studies of the Uranyl Carbonate Mineral Andersonite, Na2Ca[(UO2)(CO3)3]·(5+x)H2O

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“…However, it seems that for the commensurate case the super-cell approach should work. The number of 12,836.18 bits/cell makes swamboite-(Nd) extraordinarily complex, one of the most complex minerals in Nature, besides ewingite [53] [47]. From the point of view of chemistry, uranyl silicates are relatively simple minerals (Table 3), none of which exceed 100 bits/formula.…”

Section: Structural and Chemical Complexity Of Uranyl Silicate Mineralsmentioning

confidence: 99%

Mineralogy, Crystallography and Structural Complexity of Natural Uranyl Silicates

Plášil

2018

Minerals

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Naturally occurring uranyl silicates are common constituents of the oxidized parts (i.e., supergene zone) of various types of uranium deposits. Their abundance reflects the widespread distribution of Si4+ in the Earth’s crust and, therefore, in groundwaters. Up to date, 16 uranyl silicate minerals are known. Noteworthy is that the natural uranyl silicates are not extremely diverse regarding their crystal structures; it is a result of possible concentrations (activity) of Si4+ in aqueous solutions derived from dissolution of primary Si minerals or the composition of late hydrothermal fluids. Therefore, in natural systems, we distinguish in fact among two groups of uranyl silicate minerals: uranophane and weeksite-group. They differ in U:Si ratio (uranophane, 1:1; weeksite, 2:5) and they form under different conditions, reflected in distinctive mineral associations. An overview of crystal-chemistry is provided in this paper, along with the new structure data for few members of the uranophane group. Calculations of the structural complexity parameters for natural uranyl silicates are commented about as well as other groups of uranyl minerals; these calculations are also presented from the point of view of the mineral paragenesis and associations.

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“…Recent uranyl carbonate mineral discoveries have uncovered remarkably complex topological arrangements that formed under restrictive conditions of Ca-U-CO 3 equilibria [1][2][3]. In part, these new minerals lend their complexity to hydrated calcium polyhedra found in their structures, which can share numerous geometrical elements with uranyl tricarbonate units (UTC), (UO 2 )(CO 3 ) 3 4− , to form multidimensional structures.…”

Section: Introductionmentioning

confidence: 99%

Paddlewheelite, a New Uranyl Carbonate from the Jáchymov District, Bohemia, Czech Republic

et al. 2018

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Paddlewheelite, MgCa 5 Cu 2 [(UO 2 )(CO 3 ) 3 ] 4 ·33H 2 O, is a new uranyl carbonate mineral found underground in the Svornost mine, Jáchymov District, Bohemia, Czech Republic, where it occurs as a secondary oxidation product of uraninite. The conditions leading to its crystallization are complex, likely requiring concomitant dissolution of uraninite, calcite, dolomite, chalcopyrite, and andersonite. Paddlewheelite is named after its distinctive structure, which consists of paddle-wheel clusters of uranyl tricarbonate units bound by square pyramidal copper "axles" and a cubic calcium cation "gearbox." Paddle wheels share edges with calcium polyhedra to form open sheets that are held together solely by hydrogen bonding interactions. The new mineral is monoclinic, Pc, a = 22.052(4), b = 17.118(3), c = 19.354(3) Å, β = 90.474(2) • , V = 7306(2) Å 3 and Z = 4. Paddlewheelite is the second-most structurally complex uranyl carbonate mineral known after ewingite and its structure may provide insights into the insufficiently described mineral voglite, as well as Cu-U-CO 3 equilibrium in general.the surface of used nuclear fuel exposed to groundwater. Uranyl carbonate minerals can record and be used to diagnose groundwater conditions at the moment of crystallization, allowing for more accurate safety assessments of U contaminated water transport and longer-term radionuclide release models for Ca-U-C systems. Here we describe the crystal-chemical and spectroscopic properties of the new Ca-Mg-Cu uranyl carbonate mineral paddlewheelite, whose structure contains several first known instances for uranyl minerals, including isolated square pyramidal copper polyhedra and calcium cations in cubic coordination. These two unique cation polyhedra bind to UTC units, forming an extraordinary paddlewheel motif arranged into an open-sheet topology that may provide several clues to understanding the structure and formation of the poorly described mineral voglite,The name paddlewheelite was chosen to reflect the unique structure of the mineral that resembles the paddlewheel of a steamboat. Four uranyl tricarbonate paddles are bound by two square pyramidal CuO 5 "axles" and a CaO 8 "gearbox" in cubic coordination. The new mineral and its name were approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA2017-098). The holotype specimen is deposited in the Natural History Museum of Los Angeles County, under catalogue number 66696. OccurrenceCrystals of paddlewheelite were collected underground from a bifurcation of the Prokop vein on the 5th level of the Svornost mine, Jáchymov District, Bohemia, Czech Republic. The Svornost mine (Einigkeit in German, Concord in English) is named for one of the six major ore clusters in the Jáchymov ore district. "Five-element" (Ni-Co-As-Ag-Bi, +/− U) mineralization was deposited there during episodic fracturing and space filling by metal-rich hydrothermal solutions. Further details regarding the geology and hydrothermal history of the J...

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Ewingite: Earth’s most complex mineral

Cited by 30 publications

References 28 publications

Structure Refinement and Thermal Stability Studies of the Uranyl Carbonate Mineral Andersonite, Na2Ca[(UO2)(CO3)3]·(5+x)H2O

Structure Refinement and Thermal Stability Studies of the Uranyl Carbonate Mineral Andersonite, Na2Ca[(UO2)(CO3)3]·(5+x)H2O

Mineralogy, Crystallography and Structural Complexity of Natural Uranyl Silicates

Paddlewheelite, a New Uranyl Carbonate from the Jáchymov District, Bohemia, Czech Republic

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